The aim of this research was to determine the adsorption behaviour of bulgur. Three different particle sizes (2 < coarse < 3.5, 1.6 < medium < 3.0, 0.5 < fine < 2.0 mm) of bulgur, purchased from market, were kept in nine different equilibrium levels of relative humidity (8.2-97.3%) at 20, 30 and 40°C. The data obtained were evaluated using BET (Brunauer-Emmett-Teller) and GAB (Guggenheim, Anderson and deBoer) sorption equations. The equilibrium moisture content of bulgur increased both with decreasing temperature and bulgur size. The constants m0 and C of BET and GAB equations were determined to be between 2.54 and 5.03 g water per 100 g of dry matter and 4.96-16.57, respectively. Constant k was between 0.85 and 0.93, and GAB equation was determined to fit very well for bulgur adsorption, because of %E values lower than 10%. Bulgur must be stored below 70% relative humidity and with less than 10 g water per 100 g of dry mater.